Dynamics of Biofilm Regrowth in Drinking Water Distribution Systems.

I Douterelo,J Boxall,S Husband,V Loza,J L Schottel

doi:10.1128/aem.00109-16

Abstract

ABSTRACTThe majority of biomass within water distribution systems is in the form of attached biofilm. This is known to be central to drinking water quality degradation following treatment, yet little understanding of the dynamics of these highly heterogeneous communities exists. This paper presents original information on such dynamics, with findings demonstrating patterns of material accumulation, seasonality, and influential factors. Rigorous flushing operations repeated over a 1-year period on an operational chlorinated system in the United Kingdom are presented here. Intensive monitoring and sampling were undertaken, including time-series turbidity and detailed microbial analysis using 16S rRNA Illumina MiSeq sequencing. The results show that bacterial dynamics were influenced by differences in the supplied water and by the material remaining attached to the pipe wall following flushing. Turbidity, metals, and phosphate were the main factors correlated with the distribution of bacteria in the samples. Coupled with the lack of inhibition of biofilm development due to residual chlorine, this suggests that limiting inorganic nutrients, rather than organic carbon, might be a viable component in treatment strategies to manage biofilms. The research also showed that repeat flushing exerted beneficial selective pressure, giving another reason for flushing being a viable advantageous biofilm management option. This work advances our understanding of microbiological processes in drinking water distribution systems and helps inform strategies to optimize asset performance.IMPORTANCE This research provides novel information regarding the dynamics of biofilm formation in real drinking water distribution systems made of different materials. This new knowledge on microbiological process in water supply systems can be used to optimize the performance of the distribution network and to guarantee safe and good-quality drinking water to consumers.

Highlights

The majority of biomass within water distribution systems is in the form of attached biofilm
It is accepted that if the hydraulic conditions in the distribution network change and overcome biofilm adhesive forces, biofilms can detach from the pipe walls, and they have the potential to impact the performance of the water infrastructure and the final quality and safety of the supplied water [1, 2]
Further research is needed to assess the impact of biofilm mobilization during the supply of drinking water, as this is known to contribute to discoloration, which is the single largest cause of customer contacts relating to water quality

Summary

Introduction

The majority of biomass within water distribution systems is in the form of attached biofilm. This research provides novel information regarding the dynamics of biofilm formation in real drinking water distribution systems made of different materials. This new knowledge on microbiological process in water supply systems can be used to optimize the performance of the distribution network and to guarantee safe and good-quality drinking water to consumers. Drinking water distribution systems (DWDS) support a diverse microbial community attached to the pipe walls where biofilms form. Biofilms are difficult and practically impossible to eliminate from DWDS surfaces due to the protection offered by the microbial self-produced extracellular polymeric substance (EPS) matrix This matrix protects microorganisms within biofilms from external adverse factors and fluctuations, including chemical disinfection [15].

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